Rust preventive film



April 1951' J. J. BROPHY ET L 2,549,050

I RUST PREVENTIVE FILM Filed March 22, 1947 2 Sheet s-Sheet 1 [nveniorsJahn Jfirophy Bernard/Zfinelea April 1951 J. J. BROPHY ET AL RUSTPREVENTIVE FILM 2 Sheets-Sheet 2 Filed March 22 194'? Inventors" 1 fiJhnJBrapQy Bernard MPZneZe Patented Apr. 17, 1951 UNITED STATES PATENTOFFlCE RUST PREVENTIVE FILM Application March 22, 1947, Serial N0.736,514

13 Claims. (Cl. 260-323) This invention relates to temporarilyprotecting an article from corrosion by means of a film or coating whichmay be readily stripped off when desired. This application is acontinuation in part of application for Letters Patent of the UnitedStates, Serial No. 533,014, filed April 27, 1944, now abandoned.

It is well known that metal surfaces, particularly ferrous metalsurfaces, are subject to corrosion possibly from the effects of moistureand oxygen in contact with them. It is desirable that a protectivecoating be applied which may be readily and quickly removed. A film oflight or low viscosity oil will protect a metal surface from corrosionfor a certain period of time but such an oil has the disadvantage thatthe liquid tends to drain 01f so that ultimately the liquid film becomesruptured. An oil of very high viscosity gives a much longer period ofprotection, but such an oil, which is ordinarily a grease at roomtemperature, is difficult to apply and diflicult to remove when it hasserved its purpose.

According to the present invention an article which is to be subjectedto conditions conducive to corrosion of the article or its contents istemporarily protected from corrosion, for example is prepared forstorage or shipment, by applying to the article a solution of afilm-forming colloid to provide a strong, tough, flexible film orcoating which adheres lightly and may be readily peeled or stripped offwhen desired, for example when it has served its purpose, said film orcoating having associated with it a corrosion inhibitor. Thefilm-forming colloid solid is preferably applied by spraying a solutionof it upon the article, although other methods of application such asdipping or brushing may be employed. Different methods of associatingthe corrosion inhibitor with the readily strippable film may beemployed. Thus there may be applied first a coating of corrosioninhibitor and then a coating of film-forming colloid; or there may beapplied first a coating, preferably a thin coating, of film-formingcolloid containing a corrosion inhibitor and; then a coating of the sameor another film-forming colloid to amalgamate with the first film orcoating so as to form an integral coating which may be readily strippedoff; or merely a coating of film-forming colloid containing a corrosioninhibitor. Preferably a single coating which contains a corrosioninhibitor is employed.

Referring to the accompanying drawings,

Fig. 1 is a perspective of a machine gun in process of having applied toit by means of a spray a temporary protective coating;

Fig. 2 is a perspective of the coated gun;

Fig. 3 is a perspective of the coated gun mounted immovably in acontainer and ready for shipment; and

Fig. 4 is a perspective of a metal article which has been coated, andthe coating slit and partly peeled or stripped off.

In Fig. 1 there is shown a machine gun I of the fixed type, that is, onewhich is designed for installation adjacent to an airplane engine. Thegun is shown as supported upside down by two spaced upright crotchedposts 9, ll (see Fig. 2), one crotch receiving the end of the barrel ofthe gun and the other crotch receiving a cylindrical member [3 at therear of the gun. So supported, the gun may be rotated to expose all ofits outer portions for application of a temporary protective coating,for example to the spray l5 which issues from a spray gun ll held in onehand by the operator and controlled by a trigger 19.

The spray gun shown is a commercial one and has two valves 2|, 23 whichmay be opened and closed by turning their knurled heads. The valve 2|does not control the flow of air through the main nozzle. It merelycontrols the flow of air through two small auxiliary nozzles 24, 25 soas to increase the proportion of air to spray material and to flattenout the spray into the fanshape shown. When the valve 2| is closed, thespray has the shape of a cone. Air is supplied to the spray gun from anair compressor (not shown) through a tube 21, there being between theair compressor and the spray gun a valve (not shown) manipulation ofwhich varies the pressure on the air. A second tube 29 leads from asource of supply under pressure (not shown) of the solution of spraymaterial to a small receptacle 3| which is fast to the spray gun, avalve (not shown) being provided for varying the pressure on the spraymaterial. The trigger l9, which the operator presses with his fingers,causes spray to issue from the main nozzle, Spraying, as has beenstated, is the preferred method by which the coating or film may beapplied, and for spraying any suitable spraying apparatus may beemployed.

It will be noted that the machine gun has various gaps or openings inits exterior. For example, the supporting jacket 13 which sur- 3 roundsthe barrel has a series of round holes 33 and the walls of the body ofthe gun which contain the firing mechanism have in them certainopenings, mostly rectangular in outline, whichare larger than the holesin the wall of the jacket. All of these holes and openings should becovered before the regular coat of spray material is applied. They maybe covered with some extraneous substance such as paper or adhesivetape. As shown, however, the opening in the bottom of the body portionof the machine gun is being bridged or covered by a fan-shaped spray theparticles of which are in the form of comparatively long filaments, theeffect of such a spray being to produce a coating of comparatively long,com paratively dry filaments arranged at random, such a coating beingreferred to hereinafter as a bridging coating. The openings may all bethus covered, after which the regular conical spray of smaller, wetterparticles is used. This negligible in that it does not interfere withstripping off the coatingwhen desired.

A composition for forming a corrosion inhibiting coating may comprise asolution of a filmforming colloid and a corrosion inhibitor in avolatile solvent. The coating is applied preferably by spraying asolution of this type on the article to be protected and evaporating thesolvent to form a tough, but readily removable, protective filmcomprising the colloid and the inhibitor. In a preferred form thecoating composition also includes a non-corrosive, non-drying oil. It isfound that the oil improves the effectiveness of the coating inpreventing cormethod of spraying, which dispenses with the use of paper,tape, etc., forms the subject-matter of application Serial No. 533,015,filed April 27, 1944, in the name of Bernard M. Pineles, now UnitedStates Patent No. 2,441,227, granted May 11, 1948. Once the openingshave been closed, either by the bridging coating or by means of paper,tape or some other extraneous material, the whole machine gun, includingthe bridging coatings or covers over the openings, is coated with theregular spray material as is shown in Fig. 2 wherein the machine gun iscompletely covered by a film or coating 35.

Although the film is tough and flexible, it may be desirable to protectit against rupturing during extraordinary rough treatment, suchrupturing being particularly liable to occur when the covered article isa heavy one such as a machine gun. The covered gun may be packaged asshown in Fig. 3. A rigid container 31, herein shown as a rectangularwooden box, is provided with supports for the covered gun in the form ofcrosspieces 39 which fit about the parts of the gun supported by them.These crosspieces, in those localities which would otherwise contactdirectly with the coating or film on the gun, are provided withsupporting faces of felt M or other soft and yielding material, the endsof the box being similarly provided so that the packaged gun may behandled roughly without danger of rupturing the film.

The coating or film which covers the articles adheres onl lightly andmay be readily peeled off in large pieces or stripped off in practicallyone piece, depending upon the contour of the article. In practice, sincethe film or coating is a strong tough one, it is customary first to slitthe film at some convenient locality and then peel or strip it off. InFig. 4 there is shown a metal article 43 which has been covered by afilm or coating and the film is in process of being removed, said filmhaving been slit or cut and partly peeled 0r stripped off.

The film or coating, as has been stated above, is. one which may bereadily peeled or stripped off when desired. It also adheres lightly tothe article and in the case of an article which is partly or entirelyenveloped, the shrinking of the coating after it has been applied actsalso to hold it in place. The film or coating adheres lightly in anycase except possibly unusual cases such as to smooth, highly polishedmetal surfaces or to the surface of a glass plate. However, the adhesionof the coating is practically rosion but that the oil is not essentialand that in many cases satisfactory corrosion prevention can be obtainedwithout it. A plasticizer is ordinarily included in the composition forits usual function of providing flexibility and resistance to cracking.The plasticizer also may be eliminated where the stress to which thecoating will be subjected is not great.

Among the suitable film-forming colloids which we have found useable inour coating composition are water-insoluble cellulose esters, includingcellulose acetate butyrate, cellulose acetate propionate, and cellulosepropionate, water-insoluble cellulose ethers, such as ethyl celluloseand benzyl cellulose, and copolymers of vinyl chloride and vinyl acetatehaving a vinyl chloride content of at least about The vinyl copolymersare particularly satisfactory because of their degree of resistance tothe passage of moisture, coupled with their capability of beingdissolved in certain readily available volatile or easily evaporablesolvents. Other film-forming colloids ma be used, but the degree ofprotection obtained will, of course, vary with the quality of thefilm'produced.

Glyceryl monolaurate has been found very effective as a corrosioninhibitor in the coating of the present invention. Other inhibitorsinclude the alkali metal and ammonium salts of fatty acids having from10 to 18 carbon atoms,

- and the products of incomplete esterification of polyhydric alcoholsand fatty acids having from 10 to 18 carbon atoms. It will be observedthat these corrosion inhibitors are at least partially water-dispersiblematerials comprising a first radical derived from a fatty acid having along hydrocarbon chain attracted to hydrocarbon oils and a secondradical which is attracted to water. The following are examples ofcompounds which have been found effective as corrosion inhibitors: 7

Sodium salt of phosphorated castor oil Sodium salt of phosphorated teaseed oil Diglycol laurate Sodium stearate Sodium oleate Sodium laurateAmmonium linoleate Ivory soap Mannitan myristate Mixtures of corrosioninhibitors may be used, a desirable mixture being'formed by the use of asmall amount of a compound quite soluble in water, such as sodiumlaurate, and a large amount of a much less soluble compound, such asglyceryl monolaurate. A particularly good mixture is a technical gradeglyceryl monolaurate containing about 9% potassium laurate and 1.5%lauric acid;

The corrosion inhibitors will be employed in the ratio of about 2.5 toabout 8 parts by weight to about parts by weight of the film-formingcolloid.

The oil employed in the coating is a noncorrosive, non-drying oil,suitably a petroleum hydrocarbon base hydraulic oil. The oil appears toact somewhat as a plasticizer and also, and possibly of greaterimportance, it appears to serve as a carrier or partial carrier for thecorrosion inhibitors since the preferred inhibitors have longhydrocarbon chain groups which are attracted to hydrocarbon oils. Itshould also be noted that the oil in the film prevents the absorption ofoil from oiled surfaces. To achieve its desired results, it is importantthat the oil remain fluid under the conditions of use. That is, the oilshould have a low viscosity, a low pour point, and a high viscosityindex. Stable hydrocarbon oils or mixtures of oils such as petroleumfractions have been found suitable. The oil will preferably be employedin the proportion of up to about 6 parts by weight of the oil to about15 parts by weight of the film-forming colloid. It is to be noted thatprotection against corrosion can be obtained with coating composi tionswhich do not include oil, although the oil does give definitely improvedprotection.

As a plasticizer for the coating, 3GH, a product of Carbide and CarbonChemicals Corporation, believed to be triethylene glycol di-2-ethylbutyrate, has been found very satisfactory, particularly with vinylresin compositions. Other compatible non-corrosive plasticizers may beused, such as 360 (triethylene glycol di-Z-ethyl hexoate) and dioctylphthalate. The preferred proportion of plasticizer is from about 2 partsto about 6 parts of the plasticizer to about 15 parts of thefilm-forming colloid. The proportion of plasticizer does not appear t becritical and the quantity employed depends on the characteristicsdesired in the coating.

Suitable solvents for forming the coatin materials are acetone,propylene oxide and methyl ethyl ketone; but any volatile organicsolvent which will dissolve the resins to give a solution of sprayableviscosity may be used. It has been found that ethylene glycol monomethylether in proportion up to about parts by weight to 100 parts of amiscible solvent for the filmforming colloid improves the ability of thecomposition to form web-like fibers when sprayed in air, notwithstandingwide variations in the humidity of the air.

Below are specific examples of spray material.

Example I Parts by weight Vinylite VYNS 15 3GH 4 Oil 1255 4 Glycerylmonolaurate 4 Acetone 85 Ethylene glycol monomethyl ether 10 VinyliteVYNS, a product of Carbide and Carbon Chemicals Corporation of New York,is a copolymer of vinyl chloride and vinyl acetate Sil /2% chloride).This film-forming colloid is more impervious to moisture than are manyof the film-forming colloidal materials and is practically insoluble inacids and alkalis.

Oil 1255, a product of the Standard Oil Company of New Jersey, is a lowtemperature, noncorrosive, non-drying petroleum base hydrocarbon oil.

Example If Parts by weight Vinylite VYNS 15 3GH 4 W. S. 491 oil 4Glyceryl monolaurate 4 Methyl ethyl ketone The W. S. 491 oil, a lowtemperature noncorrosive, non-drying petroleum hydrocarbon oil, is aproduct of the Standard Oil Company of New Jersey.

Example III Parts by weight Vinylite VYHI-l 15 3GH 4 Oil 1255 4 Glycerylmonolaurate 4 Methyl ethyl ketone 45 Vinylite VYHH, a product of theCarbide and Carbon Chemicals Corporation of New York, is a copolymer ofvinyl chloride and vinyl acetate (85 to 88% chloride) having a molecularweight in the range of about 10,000. Since Vinylite VYHH has a lowermolecular weight than Vinylite VYNS, it is more soluble. Particularlygood bridging coatings may be formed with Example I given above.

Example IV Parts by weight Cellulose acetate butyrate 15 3GH 4 W. S. 491oil 4 Glyceryl monolaurate 4 Methyl ethyl ketone 135 Example V Parts byweight Ethocel, l0 cps, medium, ethoxy content l5 3GH 4 W. S. 491 oil 4Glyceryl monolaurate l- 4 Methyl ethyl ketone 135 Ethocel 10 cps, mediumethoxy content, is a product of the Dow Chemical Company of Midland,Michigan.

Although each of the examples given employs glyceryl monolaurate as acorrosive inhibitor, other corrosion inhibitors of the class disclosedhave been found very satisfactory and when substituted for an equalamount of glyceryl monolaurate in Example I have withstood the followingtest as has the material of Example I.

Cold rolled steel plates two inches wide, three inches long andone-eighth inch in thickness were polished with a built-up glued alundumpolishing wheel after which they were sandblasted. They were washed witha 5% to 10% solution of trisodium phosphate and rinsed with tap wateruntil free from alkali. They were then rinsed in succession withdistilled water, ethyl alcohol and isopropyl alcohol followed byabsolute alcohol (methyl, ethyl or isopropyl), and dried in a dessicatorover calcium chloride. All the above operations were carried out asrapidly as possible. The plates taken from the dessicator wereimmediately coated by means of a spray. After having dried over night,the plates, protectively coated in accordance with the invention, weresubjected to two tests known respectively as the fresh water test andthe salt spray test. The plates were hung in vertical position on glasshooks (a) in a humidity cabinet at 100 F. and 100% relative humidity for200 hours and (b) for the same length of time in a cabinet at the sametemperature which was filled with a salt spray made by aspirating a 20%salt solution. At the ends of the tests, the plates in each case were inperfect condition, and the films were tough and somewhat oily on theirinner surfaces.

In using as a spray material any of the solutions given above thespraying is done at room temperature and a large part of the solvent islost by evaporation as the particles of spray travel from their point offormation to the article. The film, as first formed, is somewhat wet butrapidly dries and becomes strong. Although solvents which are easilyevaporable and dissolve the film-forming colloid at room temperaturehave been given above, it should be understood that heat may be usedwith such solvents as well as with liquids which are solvents only atelevated temperatures. The temperatures and pressures used as well asthe distance of the nozzle of the spray gun from the article to becoated may, of course, vary widely. In the examples given, the followingwill be found convenient: pressure on air about 30 lbs. per square inch;pressure on spray material about 15 lbs. per square inch; distance fromnozzle of gun to article with regular spray 4 or.5 inches, 7

with bridging spray 14 or 15 inches. The corrosion inhibitors are greasycompounds and because of their presence in the film or coating togetherwith that of the oil, the film or coating has a, slightly oily or greasysurface which prevents firm adhesion of the film to the article.

Where there are no wharves or other facilities for landing freight fromships, for example, where the shore is sandy and the water is shallow,it is necessary to dump articles of freight into the sea at high tide asnear as possible to the shore and then at low tide to rescue thearticles. These articles, which are likely to have been exposed to humidatmospheres and to have been roughly handled by inexperiencedstevedores, are more roughly handled, so to speak, by the waves and thetide and are exposed to salt water and to a salty and usually very humidatmosphere with the result that, even if corrosion of the metal articleshas been prevented up to the time that the packaged articles were dumpedinto the sea, corrosion is likely to occur before the articles can bebrought ashore.

A corrodible metal article prepared for ship- I ment by being coatedwith a film and packed in a rigid container as described above, may bedumped into the sea on a sandyshore and allowed to be washed around bythe waves and intermittently exposed to the atmosphere by the ebbing ofthe tide for a considerable period without danger of being corroded. Intests, machine guns, properly oiled and in condition for immediate useandprepared as above for shipment including the use of the formula ofExamplel, have been anchored at half tide to asandy bottom bya ropewhich was long enough to permit the packaged gun to be rolled about bythe waves and the tides, the rigid container being perforated, to makethe test more severe, so as to permit free entrance of water and sand.Such packaged guns have been allowed to remain exposeo at alternateintervals to sea water and to the atmosphere for periods as long as fourweeks; and; when the covered guns were removed from their rigidcontainers and the films 'slit and stripped off, said guns were freefrom corrosion and were immediately placed on mounts and fired. Althoughpackaged machine guns have been discussed above, various othercorrodible articles were also subjected to the same test. Among others,a radio set mounted in a wooden case was enveloped in the film andpacked in a Wooden box in which holes were bored. At the end of fourweeks exposure at intervals to sea water and the atmosphere, the box wastaken from the sea, the covered radio set was taken from the box, thefilm or coating was stripped oil, and the set was immediately connectedto a source of electric power. It operated perfectly.

'It is not necessary that the film or coating should be applied directlyto a corrodible article in order to protect it against corrosion. Forexample, if a steel plate is placed in a receptacle made of materialsuch, for example, asglass, which is impervious to moisture, saidreceptacle having an open mouth and this mouth is covered by a film ofmaterial containing a rust inhibitor and the covered receptable placedin an atmosphere of 100 F. and 100% relative humidity, corrosion of thesteel plate will be prevented for along period. Apparently any watervapor which passes through the film into the receptacle carries with itsome of the corrosion inhibitor and as long as there is a sufficientsupply of corrosion inhibitor in the film, corrosion of the plate willbe prevented. Of course, similar protection against corrosion may beprovided if the metal article is wrapped say in paper'and then thepackage is enveloped in a film which carries a supply of corrosioninhibitor.

Many corrosion inhibitors will not standthe rather severe tests whichhave been given above but will all serve as corrosion inhibitors atcertain temperatures and relative humidities and for certain periods oftime. There are, of course, a large number of substances which act moreor less efficiently as corrosion inhibitors, the corrosion inhibitor andthe film-forming colloid chosen depending upon the temperature andhumidity to which the corrodible article is to be exposed and the lengthof time for which protection is requred. In any case .it will be notedthat a surplus supply of corrosion inhibitor is maintained in proximityto the metal article which is to be protected. Just what takes place isnot known but very possibly any moisture which passes through the filmor coating picks up and carries with it some of the inhibitor so that aslong as there is an adequate supply of inhibitor available corrosionwill be prevented. The prevention of corrosion for long periods or timeis thus due apparently to the fact that the film or coating hasassociated with it a surplus supply of corrosion inhibitor which becomesavailable as needed.

Although the invention has been described in connection with spraying afilm-forming colloidal material containing a corrosion inhibitor upon anarticle which is to be temporarily protected, it should be noted that aseparate film or sheet can be made as an article of manufacture, ifdesired, for example by spraying a coating upon a smooth surface, suchas that of glass, and then peeling off the resulting sheet. Such a sheetmay be used in packaging an article, for example, as set forth inapplication Serial No. 528,133, filed March 25, 1944, in the name ofRobert W. Lamover them a'protective coating and retains them in place onthe sheet.

Having described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. A moisture-corrodible article having thereon a temporary protectivecoating highly resistant to passage of moisture, said coating comprisinga non-corrosive, non-drying hydrocarbon oil in quantity not exceeding 6parts by weight, 15 parts by weight of a water-insoluble, film-formingcolloid from the group consisting of cellulose esters, cellulose ethersand copolymers of vinyl chloride and vinyl acetate containing at least85% of vinyl chloride, 2.5 to 8 parts by weight of a corrosion inhibitorfrom the group consisting of at least partially water-dispersible alkalimetal and an1- monium salts and incompletely esterified polyhydricalcohol esters of fatty acids having from to 18 carbon atoms, saidcoating being capable of being readily stripped off.

2. A moisture-corrodible article having thereon a temporary protectivecoating highly resistant'to passage of moisture, said coating comprisingfrom 4 to 6 parts by weight of a non-corrosive, nondrying hydrocarbonoil, parts by weight of a water-insoluble, film-forming colloid from thegroup consisting of cellulose esters, cellulose ethers and copolymers ofvinyl chloride and vinyl acetate containing at least 85% of vinylchloride, from 2 to 6 parts by weight of a compatible, noncorrosiveplasticizer for the film-forming colloid, and 2.5 to 8 parts by weightof a corrosion inhibitor from the group consisting of at least partiallywater-dispersible alkali metal and ammonium salts and incompletelyesterified polyhydric alco hol esters of fatty acids having from 10 to18 carbon atoms, said coating being capable of being readily strippedoff.

3. A moisture-corrodible article having thereon a temporary protectivecoating highly resistant to passage of moisture, said coating comprisingfrom 4 to 6 parts by weight of a non-corrosive, nondrying hydrocarbonoil, 15 parts by weight of a water-insoluble, film-forming colloid fromthe group consisting of cellulose esters, cellulose ethers andcopolymers of vinyl chloride and vinyl acetate containing at least 85%of vinyl chloride, and 2.5 to 8 parts by weight of glyceryl monolaurate,said coating being capable of being readily stripped off.

4. A moisture corrodible article having thereon a temporary protectivecoating highly resistant to passage of moisture, said coating comprisingthe following ingredients in the following amounts:

Parts by weight Copolymer of vinyl chloride and vinyl acetate containingat least 85% vinyl chloride 15 Compatible, non-corrosive plasticizer forthe copolymer 4 A non-drying, non-corrosive hydrocarbon oil- 4 Glycerylmonolaurate 4 5. A liquid, freely flowing composition comprising anon-corrosive, non-drying hydrocarbon oil in quantity not exceeding 6parts by weight, 15 parts by weight of a water-insoluble, film-formingcolloid from the group consisting of cellulose esters, cellulose ethersand copoymers of vinyl chloride and vinyl acetate containing at least85% of vinyl chloride, and from 2.5 to 8 parts by weight of a corrosioninhibitor from the group consisting of at least partiallywater-dispersible alkali metal and ammonium salts and incompletelyesterified polyhydric alcohol esters of fatty acids having from 10 to 18carbon atoms, all dissolved in a volatile organic solvent.

6. A liquid, freely flowing composition comprising from 4 to 6 parts byweight of a non-corrosive, non-drying hydrocarbon oil, 15 parts byweight of a water-insoluble, film-forming colloid from the groupconsisting of cellulose esters, cellulose ethers and copolymers of vinylchloride and vinyl acetate containing at least of vinyl chloride, from2.5 parts to 8 parts by weight of a corrosion inhibitor from the groupconsisting of at least partially water dispersible alkali metal andammonium salts and incompletely esterified polyhydric alcohol esters offatty acids having from 10 to 18 carbonatoms, and from 2 to 6 parts byweight of a compatible, non-corrosive plasticizer for the film-formingcolloid, all dissolved in a volatile organic solvent.

'7. A liquid, freely flowing composition comprising from 4 to 6 parts byweight of a noncorrosive, non-drying hydrocarbon oil, 15 parts by weightof a water-insoluble, film-forming colloid from the group consisting ofcellulose ethers, cellulose esters and copolymers of vinyl chloride andvinyl acetate containing at least 85% of vinyl chloride, and from 2.5 to8 parts by weight of glyceryl monolaurate, all dissolved in a volatileorganic solvent.

8. A liquid, freely flowing composition having the following ingredientsin the following amounts: 1

Parts by weight Copolymer of vinyl chloride and vinyl acetate containingat least 85% vinyl chloride--- 15 Compatible, non-corrosive plasticizerfor the copolymer 4 A non-drying non-corrosive hydrocarbon oil. 4Glyceryl monolaurate 4 Volatile organic solvent containing about 88%vinyl chloride 15 Compatible, non-corrosive plasticizer for thecopolymer 4 A non-drying, non-corrosive hydrocarbon oil. 4 Glycerylmonolaurate i A mixed solvent of which 10 parts by weight is ethyleneglycol monomethyl ether and 85 parts by weight is acetone 95 10. Apellicle for protecting a moisture-corrodible article from corrosioncomprising a sheet highly resistant to passage of moisture, the sheetbeing formed of a mixture of a non-corrosive, non-drying hydrocarbon oilin quantity not exceeding 6 parts by weight, 15 parts by weight of awater-insoluble, filrn-forrhing colloid from the group consisting ofcellulose esters, cellulose ethers and copolymers of vinyl chloride andvinyl acetate containing at least 85% of vinyl chloride, and 2.5 to '8parts by weight of a corrosion inhibitor from the group consisting of atleast partially water-dispersible alkali metal and ammonium salts andincompletely esterified polyhydric alcohol esters of fatty acids havingfrom 10 to 18 carbon atoms.

11. A pellicle for protecting a moisture-corrodible article fromcorrosion comprising a sheet highly resistant to passage of moisture,the: sheet being formed of a mixture of from 4 to 6 parts by weight of anon-corrosive, non-drying hydrocarbon oil, 15 parts by weight of awater-insoluble,

1'! film-forming'colloid from the group consisting: of cellulose esters,cellulose ethers and copolymers of vinyl chloride and vinyl acetatecontaining at least 85% of vinyl chloride, from 2 to 6 parts by Weightof a compatible, non-corrosive plasticizer for the film-forming colloid,and 2.5 to- 8 parts by Weight of a corrosion inhibitor from the groupconsisting of at least partially Water-dispersible alkali metal andammonium salts and incompletely esterified' polyhydric alcohol esters offatty acids having from 10 to 18 carbon atoms.

12. A pellicle for protecting a moisture-corrodible article fromcorrosion comprising a sheet highly resistant to passage of moisture,the sheet being formed of a mixture of from 4 to 6 parts by Weight of anon-corrosive, non-drying hydrocar bon oil, 15 parts by Weight of aWater-insoluble, film-forming colloid from the group consisting ofcellulose esters, cellulose ethers and copolymers of vinyl chloride andvinyl acetate containing at least 85% of vinyl chloride, and 2.5 to 8parts by Weight of glyceryl monolaurate.

13. A pellicle for protecting a moisture-corrodible article fromcorrosion comprising a sheet highly resistant to passage of moisture,the sheet comprising the following ingredients in the following amounts:7

Parts by Weight Copolymer of vinyl chloride and vinyl acetate JOHN J.BROPHY. BERNARD M. PINELES. ROBERT C; PUTNAM.

REFERENCES CITED The following references are of record in the fiieofthis patent:

UNITED STATES PATENTS 20' Number Name Date 1,776,368 Novotny Sept. 23,1938 2,337,424 Stoner et al Dec. 21, 1943 SoWa Jan. 11, 1944

7. A LIQUID, FREELY FLOWING COMPOSITION COMPRISING FROM 4 TO 6 PARTS BYWEIGHT OF A NONCORROSIVE, NON-DRYING HYDROCARBON OIL, 15 PARTS BY WEIGHTOF A WATER-INSOLUBLE, FILM-FORMING COLLOID FROM THE GROUP CONSISTING OFCELLULOSE EHTERS, CELLULOSE ESTERS AND COPOLYMERS OF VINYL CHLORIDE ANDVINYL ACETATE CONTAINING AT LEAST 85% OF VINYL CHLORIDE, AND FROM 2.5 TO8 PARTS BY WEIGHT OF GLYCERYL MONOLAURATE, ALL DISSOLVED IN A VOLATILEORANIC SOLVENT.